Light emitting diodes (LEDs) have been utilized since about the 1960s. However, for the first few decades of use, the relatively low light output and narrow range of colored illumination limited the LED utilization role to specialized applications (e.g., indicator lamps). As light output improved, LED utilization within other lighting systems, such as within LED “EXIT” signs and LED traffic signals, began to increase. Over the last several years, the white light output capacity of LEDs has more than tripled, thereby allowing the LED to become the lighting solution of choice for a wide range of lighting solutions.
LEDs exhibit significantly optimized characteristics for use in lighting fixtures, such as source efficacy, optical control and extremely long operating life, which make them excellent choices for general lighting applications. LED efficiencies, for example, may provide light output magnitudes that may exceed 100 lumens per watt of power dissipation. Energy savings may, therefore, be realized when utilizing LED-based lighting systems as compared to the energy usage of, for example, incandescent, halogen, compact fluorescent and mercury lamp lighting systems. As per an example, an LED-based lighting fixture may utilize a small percentage (e.g., 10-15%) of the power utilized by an incandescent bulb, but may still produce an equivalent magnitude of light.
LEDs may be mounted to a printed circuit board (PCB), which may include conductive regions (e.g., conductive pads) and associated control circuitry. The LED control terminals (e.g., the anode and cathode terminals of the LEDs) may be interconnected via the conductive pads, such that power supply and bias control signals may be applied to transition the LEDs between conductive and non-conductive states, thereby illuminating the LEDs on command.
The photometric distribution of a forward-biased LED may produce an omnidirectional pattern of light (e.g., a 180 degree spread of light emanating in all directions from a surface of the PCB upon which the LED is mounted). In order to modify such an omnidirectional photometric distribution, a plastic dome (e.g., an injection molded acrylic plastic cover) may be placed over the LED. In so doing, for example, the plastic dome may modify the photometric distribution pattern from that of an omnidirectional pattern to one of a non-omnidirectional pattern (e.g., a 120 degree spread of light emanating from a surface of the PCB). A lens may be mounted forward of the LED to further control the photometric distribution of the LED.
A system of one or more LEDs and associated lenses may, for example, be implemented within an LED-based lighting system. Each LED of such a system, however, may exhibit a photometric distribution such that the light emitted by one LED may be projected into one or more lenses that may be associated with one or more adjacent LEDs. In such an instance, for example, one lens may receive the light generated by one or more adjacent LEDs (e.g., interference light), which may adversely affect the pattern of light projected by the LED-based lighting system.
Efforts continue, therefore, to develop a multiple LED lighting system that reduces adverse interference light.